The present invention relates to a single-side-molded semiconductor device, which includes a wiring substrate having a ball grid array (BGA) arranged on the lower surface and a semiconductor chip molded with a resin encapsulant on the upper surface. The present invention also relates to a method for fabricating the device.
A semiconductor device of the BGA type has been available as a semiconductor device of an area array type. In the BGA type semiconductor device, a semiconductor chip is mounted and molded with a resin encapsulant on the upper surface of a substrate, and ball electrodes are attached to the lower surface thereof.
FIG. 12 is a plan view illustrating a known semiconductor device of the BGA type. FIG. 13 is a bottom view illustrating the known BGA type semiconductor device. FIG. 14 is a cross-sectional view thereof taken along the line XIVbxe2x80x94XIVb in FIG. 12.
As shown in FIGS. 12, 13 and 14, the known semiconductor device includes a wiring substrate 103, wiring electrodes 101, a semiconductor chip 104, metal fine wires 105, ball electrodes 102 and a resin encapsulant 106. The wiring substrate 103 is made of an insulating resin. The wiring electrodes 101 are formed on the wiring substrate 103. The semiconductor chip 104 is mounted on the wiring substrate 103 with the principal surface of the semiconductor chip 104 facing upward. Electrode pads (not shown) formed on the semiconductor chip 104 and the wiring electrodes 101 are electrically connected to each other with the metal fine wires 105. The ball electrodes 102 are formed on the lower surface of the wiring substrate 103. The resin encapsulant 106 is provided on the upper surface of the wiring substrate 103. The semiconductor chip 104, wiring electrodes 101, metal fine wires 105 and the like are molded with the resin encapsulant 106 on the upper surface of the wiring substrate 103. Although not shown in FIG. 14, external pad electrodes are formed on the lower surface of the wiring substrate 103. The external pad electrodes are electrically connected to the wiring electrodes 101 through the substrate. The ball electrodes 102 are formed on the external pad electrodes.
The known semiconductor device has an approximately rectangular planar shape and the adjacent side faces thereof are perpendicular to each other. The outer shape has been determined so that the fabrication process of the semiconductor device can be simplified. Also, marks 107 representing product name, product number, model number, manufacturer name, and symbol, for example, are inscribed on the upper surface of the resin encapsulant 106 by a laser marking process step.
In addition, in the known semiconductor device, the ball electrodes 102 attached to the wiring substrate 103 are solder balls. The solder balls are attached to the wiring substrate 103 so that the overall semiconductor device can be highly reliably mounted and bonded onto a motherboard. Also, as shown in FIG. 14, the ball electrodes 102 are arranged on the lower surface of the wiring substrate 103 in a latticed shape.
Next, the fabrication process of the known semiconductor device will be described. FIGS. 15A and 15B are respectively a plan view and a bottom view illustrating a wiring substrate in the known semiconductor device. FIGS. 16A and 16B are plan views illustrating a substrate preparation process step and a die bonding process step, respectively, in the fabrication process of the known semiconductor device. FIGS. 17A and 17B are plan views illustrating a wire bonding process step and a resin molding process step, respectively, in the fabrication process of the known semiconductor device. FIG. 18 is a plan view illustrating a cutting process step in the fabrication process of the known semiconductor device.
As shown in FIGS. 15A and 15B, the multiple wiring electrodes 101 are formed on the upper surface of the wiring substrate, and external pad electrodes 107 are formed on the lower surface of the wiring substrate. The external pad electrodes 107 are electrically connected to the wiring electrodes 101 through the substrate. The ball electrodes will be attached to the external pad electrodes 107 in the subsequent process step. The wiring substrate is a large-sized substrate on which multiple semiconductor chips will be mounted and which will be separated into individual semiconductor devices. The broken lines shown in FIGS. 15A and 15B are cutting lines, which will be used to separate the substrate into the individual semiconductor devices. Also, in each of the regions defined by the cutting lines in FIG. 15A, a central area surrounded by each array of the wiring electrodes 101 is a chip mounting area where each of the semiconductor chips is mounted by bonding.
First, the wiring substrate with the structure shown in FIGS. 15A and 15B is prepared in the substrate preparation process step shown in FIG. 16A.
Next, each of the semiconductor chips 104 is bonded, with an adhesive, onto each of the chip mounting areas of the wiring substrate in the die bonding process step shown in FIG. 16B.
Subsequently, the electrode pads (not shown) formed on the principal surface of each of the semiconductor chips 104 and their associate wiring electrodes 101 formed on the wiring substrate are electrically connected to each other with the metal fine wires 105 in the wire bonding process step shown in FIG. 17A.
Then, the members disposed on the upper surface of the wiring substrate, e.g., the semiconductor chips 104, wiring electrodes 101, metal fine wires 105, are transfer-molded with the resin encapsulant 106 in the resin molding process step shown in FIG. 17B. Thereafter, the marks 107 such as product name, product number, model number, manufacturer name, and symbol, for example, are inscribed on the upper surface of the resin encapsulant 106 for each of the semiconductor devices by a laser marker. The wiring electrodes 101 and semiconductor chips 104 are indicated by the broken lines in FIG. 17B. However, the metal fine wires 105 are not shown in the figure.
Next, in the cutting process step shown in FIG. 18, the wiring substrate having the upper surface entirely molded with the resin encapsulant 106 is cut along the cutting lines using a rotary blade, thereby obtaining individual semiconductor devices 109 of the BGA type. Hence, the semiconductor devices 109 with the structure shown in FIGS. 13 and 14 can be obtained.
In this example, the wiring substrate is cut, using the rotary blade, along the cutting lines indicated by the broken lines shown in FIGS. 15A and 15B. In this manner, the individual semiconductor devices can be obtained accurately. Normally, the separation by the rotary blade is performed using a dicing machine used in the fabrication process of the semiconductor device. Also, in the cutting process step, the wiring substrate is cut from either the lower surface or the resin encapsulant 106 side thereof.
In the subsequent process step, which is not shown, in each of the individual semiconductor devices 109, solder balls are attached to the external pad electrodes 107 formed on the lower surface of the wiring substrate 103. In this manner, the multiple ball electrodes are formed and will be used as external terminals.
The process steps for fabricating the known BGA type semiconductor device have been performed in the above-described manner, i.e., the large-sized substrate on which the multiple semiconductor chips can be mounted is used. Then, a large number of semiconductor chips are mounted on the substrate, the associate members are electrically connected, the members on the wiring substrate are molded with the resin encapsulant, and the marking is performed. Thereafter, the wiring substrate is cut into the individual semiconductor devices of the BGA type in the end.
Particularly, the marking process step is performed after the members disposed on the upper surface of the wiring substrate have been molded with the resin encapsulant 106. The marks are inscribed on the upper surface of the resin encapsulant 106 for each of the semiconductor devices by the laser marker in the process step shown in FIG. 17B.
However, it is inefficient to inscribe the marks by using the laser marker for each of such a large number of semiconductor devices, thus becoming an obstacle to increase in productivity in the assembly process. Also, depending on environments, the laser marks inscribed on the upper surface of the resin encapsulant sometimes have a low visibility and might be misidentified.
An object of this invention is to provide 1) a semiconductor device of the BGA type, which is easy to handle and which can be fabricated at low cost, by taking measures to put highly visible marks on a large number of semiconductor devices by a single process step, and 2) a method for fabricating the device.
An inventive semiconductor device includes: a wiring substrate; a semiconductor chip; an electrode; a connecting member; a resin encapsulant; and a mark member. The wiring substrate includes a wiring electrode and an external electrode, respectively, on the upper surface and the lower surface of the wiring substrate. The external electrode is to be electrically connected to the wiring electrode. The semiconductor chip is mounted on the wiring substrate. The electrode is formed on the semiconductor chip. The connecting member is used to connect the electrode of the semiconductor chip and the wiring electrode on the wiring substrate electrically to each other. The resin encapsulant molds the wiring substrate, the semiconductor chip, the connecting member and the wiring electrode. The mark member is visible and is embedded in the upper surface of the resin encapsulant.
According to the present invention, the mark member is embedded in the upper surface of the resin encapsulant. Thus, the visibility of the mark increases.
In one embodiment of the present invention, the device preferably further includes a ball electrode which is attached to the external electrode of the wiring substrate.
An inventive method for fabricating a semiconductor device includes the step of a) preparing a wiring substrate, which includes a wiring electrode and an external electrode, respectively, on the upper surface and the lower surface of the wiring substrate. The external electrode is to be electrically connected to the wiring electrode. The method further includes the step of b) mounting semiconductor chips on the wiring substrate. The method further includes the step of c) connecting an electrode of each of the semiconductor chips and the wiring electrode on the wiring substrate electrically to each other with a connecting member. The method further includes the step of d) disposing the wiring substrate on a face of one die of a molding die after the step c) has been performed; disposing a transfer sheet, on which a mark member has been formed, on a face of the other die of the molding die; and performing a resin molding process. The method further includes the step of e) removing the transfer sheet and embedding the mark member in the upper surface of a resin encapsulant by transcription, after the step d) has been performed.
According to the present invention, the mark is formed quickly by a single transfer method. Therefore, the fabrication cost can be reduced and the mark can be formed efficiently.
In one embodiment of the present invention, in the step e), the wiring substrate may be separated into individual semiconductor devices by using a rotary blade.
In another embodiment of the present invention, a ball electrode may be attached to the external electrode on the lower surface of the wiring substrate between the steps d) and e). In such an embodiment, a semiconductor device of the BGA type can be fabricated easily.
In still another embodiment, in the step a), the wiring substrate, on which the semiconductor chips can be mounted and which can be separated into individual semiconductor devices, is preferably prepared.
In still another embodiment, in the step d), a side of the transfer sheet may face the wiring substrate and the transfer sheet may be airtightly fixed on the face of the die of the molding die. The side includes the mark member formed thereon.
In still another embodiment, in the step d), the transfer sheet preferably includes the mark member formed thereon that is visible and that can be separated from the transfer sheet.